Comparison of volatile leaf terpenoids from Lippia dulcis (Verbenaceae) obtained by steam distillation and pentane liquid extraction

Comparison of pentane extraction and steam distillation of intact leaves of Lippia dulcis (hierbia dulce, ex Mexico) yielded 2.13% (DW basis) vs. 0.13% for pentane extraction (18 h, shaking). Analyses of the oils showed (pentane; distilled): camphor (33.9, 21.2%), camphene (1.8, 12.7%), 6-methyl-5hepten-2-one (7.9, 3.4%), (+)-hernandulcin, the sweet sesquiterpene (9.2, 5.9%), 3-methyl-2cyclohexene-1-one (2.7, 0.4%). The differences in hernandulcin by extraction method seems to be due to the different effects of pentane solvent on intact leaves (vs. steam volatilization by distillation). The pentane extract was also high in free, long chain fatty acids such as linoleic, hexadecanoic, and octadecanoic acids. Quantative data are presented for 72 components. Varying GC injector temperature from 100°C to 220°C revealed degradation of hernandulcin between 200°C and 220°C. Published on-line www.phytologia.org Phytologia 96(3): 252-259 (July 1, 2014). ISSN 030319430